Моделирование бизнес-процессов / Моделирование бизнес-процессов / I D E F / IDEF1MR-part1

IDEF is a method, Architecture is a means and improving manufacturing productivity is the end which the ICAM Program is pursuing within the U.S. aerospace industry.

The following material is a discussion of the fundamental concepts, techniques and procedures regarding the use of IDEF1 to produce an information model.

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Section 2.0 IDEF1 Concepts

1:M Relation

M:1 Relation

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2.0IDEF1 Concepts

2.1Introduction

This manual is designed to serve as an introduction to and reference guide for the IDEF1 information modeling methodology. The conceptual and tangible aspects of the methodology are described, displayed, and depicted in various examples throughout this manual. The IDEF1 modeling methodology incorporates basic principles into a specified process to produce an information model. This is accomplished through the efforts of selected individuals who serve specific capacities, or roles. Each of these roles has a specific set of functions which ensure the constant an continual evolution of the model. Each evolutionary phase is designed to produce certain products along the way. The development of these products is done in accordance with the prescribed procedures, through the efforts being conducted by the roles being served, and eventually equates to a detailed information model.

This reference manual will focus its attention on the role of the modeler and the conduct of the modeler’s responsibilities. It will define what an information model is and how one is built, primarily from the modeler’s perspective.

The need for the IDEF1 method became clear as the difficulty in designing integrated manufacturing systems became more and more apparent. Controlling and coordinating integration of manufacturing information often appears to be virtually impossible. Manufacturing operations tend to be so diverse that the real requirements to be placed on an integration effort are simply “buried” in all the complexity.

From an extensive and detailed examination of available manufacturing and engineering practices and the kinds of problems cited above, it was concluded that the most practical way to approach the problem of integration of manufacturing information was to develop an information requirements model prior to designing and building the corresponding information system. The IDEF1 method for developing such models was designed to reflect the integration of manufacturing information within the overall manufacturing enterprise. The IDEF1 approach is to:

1.Build an integrated information model.

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2.Design database(s) from the information model.

3.Implement and install the data base(s) and associated functional and procedural components.

The IDEF1 method offers a set of rules and procedures for creating information models. It incorporates the necessary graphics, text, and forms to inject an organized discipline into the process. It provides for the measurement and control of the progressive development of the model through the routine of the modeling discipline.

Because the modeling discipline involves an evolutionary process, the IDEF1 method is organized into stages with measurable results and specific products. It develops toward a more exact definition with each iteration. It provides a modularity, in both practice and product, that cannot be found in other methods, and that protects against the incompleteness, imprecision, inconsistencies, and inaccuracies so often encountered.

There are two fundamental components of an information model:

1.Diagrams – The structural characteristics of the information model, displayed in accordance with a set of rules and procedures that construct a meaningful representation of information.

2.Dictionary– The meaning of each element of the model reflected through the compendium of text and indices that clearly define the information reflected in the model.

An IDEF1 model involves the entire manufacturing organization. There are several roles that have to be fulfilled to conduct a successful modeling effort. This manual is principally geared toward the benefit of the Modeler, or “recorder” of the model. The Modelers teammates are: the Project Manager, the Source(s); the Reviewer(s); and the Review Committee.

The Modeler is a modeling expert. The employment of the techniques, the maintenance of the momentum, the organization and publication of data, and, in general, the production of the model are the responsibility of the Modeler. The shape of the information structure of a manufacturing activity (its architecture) as represented in the model, is the primary responsibility of the other team members.

An IDEF1 information model is a reflection of the total manufacturing enterprise and provides a baseline definition of that organization’s informational needs. It ensures that the

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information can be shared and that the information system of the total enterprise is integrated.

IDEF1 is a new methodology which addresses the many problems cited above with a structured, broad-based, fresh approach. An information model is an attempt to determine “what is needed” in terms of information, for a manufacturing enterprise, and to represent this graphically as modular units of detail. An information model provides a precise, accurate, and concise description of the information needed by a manufacturing enterprise. It has a formal character, which provides for a precise understanding of the information it portrays and it is a tool which has practical value whether or not the manufacturing enterprise is heavily committed to the use of computers. It is of optimum value to the enterprise struggling with the problem of integrated system design.

2.2Roles

The participants in an information modeling effort are grouped into five roles. Individuals who are involved in the modeling may each fulfill several roles, but each role is dealt with distinctly and should be clearly separated in the minds of the participants. The Project Manager guides the project. The Modeler, or author, is the recorder of the model. Sources provide the information for the model. Experts are individuals who validate the model. The Review Committee acts as an arbitrator in times of dispute and determines the final acceptability of the end product.

Each role may be filled by several individuals. In most cases, the workload of a role may be distributed across several participants, but in the cases of the project manager and the modeler, there must be a lead, or principal individual, who fulfills the role. This allows for the distribution of responsibility and the resolution of lines of authority throughout the modeling effort. Further, while it is the modeler’s ultimate goal to have the model approved by the review committee, the modeler reports to the project manager, not the review committee.

In this way, the otherwise conflicting interests of the modeler, review committee, and project manager, are somewhat disentangled. The project manager is always placed in a position of control, while the various technical discussions and approvals are automatically delegated to the qualified agency under that control. Figure 2-1 illustrates the relationship of the various roles.

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Reviewer

Committee

Figure 2-1. Functional Organization

2.3Multi-Phase Development

The development process of the information modeling technique is composed of five phases. Each of these phases is described below:

1.Phase Zero – Phase Zero is the context-setting phase. During this phase, the scope of the model is defined and its objectives are stated.

2.Phase One – The objective of Phase One is to define the Entity Classes which are readily apparent at this stage of the model development.

3.Phase Two – The objective of Phase Two is to define the Relation Classes which exist between the entity classes of which the model is comprised at this level.

4.Phase Three – The objective of this phase is to identify the Key Classes for each Entity Class of which the model is comprised at this time and to define each Attribute Class which is used in a Key Class.

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5.Phase Four – The objectives of this phase are to identify which Non-Key Attribute Classes should be associated with which entity classes in the model and to fully define each of these Non-Key Attribute Classes.

It is necessary to re-emphasize that the process of developing an information model is iterative in nature; that is, the model evolves from one stage to another. It is not until completion of Phase Four that the basic structural characteristics of the information resident within the scope of the model, as defined in Phase Zero, are complete.

The construction of an information model requires that a discipline and coordinated teamwork be employed daily. Teamwork means constant and effective communication among all participants in the modeling project. A regular process of critical reviews, with written comments from readers of the material, is the single most important activity in early detection of errors and the evolution of a sound model. Decisions can be made in the context of the discovered need, recorded as they unfold, and challenged while alternatives are still available. Oversights can be spotted before they cause a major disruption or critical misinterpretation. However, for the review process to work, it must not wait until the document is formally published or approved. The review process must be an everyday working procedure, conducted throughout all phases of model development.

2.4Cyclical Activities

There are three kinds of interchange cycles evident in the IDEF1 technique:

1.Data collection cycle

2.Validation cycle

3.Acceptance review cycle

Each of these cycles can occur multiple times throughout the life of the modeling project.

The Data Collection Cycle is initiated in Phase Zero. Its purpose is to establish a baseline of documentation from which to extract the fundamental nature of the information represented in the model. It is not unusual for the modeler, during later phases, to return to the sources of this documentation to clarify certain aspects of it. This is why the Data Collection Cycle is viewed as a “recurrent,” rather than a “one time,” activity.

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The validation cycle is sometimes called the IDEF Kit Cycle. The author (modeler) of the information model should have several readers review the evolving model at various stages before it is presented for acceptance. The written comments made by these reviewers should be incorporated into the model and the process should be repeated until the desired results are achieved. This is the substance of the IDEF Kit Cycle. The modeler is the draftsman; the reviewers are the architects.

The modeling effort is a continuous cycle of the synthesis of comments and findings. Certain analytical efforts must be performed at various stages along the way, but the final model description and structure is the result of a series of synthesized reviewer comments and observations.

The Acceptance Review Cycle is where a panel of experts evaluates the evolving (or fully evolved) information model to determine its acceptability for the purpose intended. This panel may require that specific areas of the model be re-validated by the experts. It may also find the model acceptable to a level (phase) of evolution reflected and simply recommend continued development. If the panel finds the model to be unacceptable, the Project Manager is required to actively resolve the points at issue to assure the development of a sound model.

Acceptance review typically occurs more than one time during a modeling project. Often, it will occur at the end of a phase, although infrequently for every phase. In all cases, a final acceptance review cycle should be conducted at the end of Phase Four.

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